Catalytic hydrogenation of organic nitrocompounds



United States Patent 3,253,039 CATALYTIC HYDROGENATIGN or ORGANIC NrrnocoMroUNns Paul N. Rylander, Newark, and Irene Karpenho, Irvington, N.Il., assignors to Engelhard Industries, inc., Newark, N.J., a corporation of Delaware No Drawing. Filed Feb. 5, 1962, Ser. No. 171,263

7 Claims. (Cl. 260-580) This invention relates to hydrogenation of organic nitrocompounds and more especially to the catalytichydrogenation of organic nitrocompounds.

The use of platinum group metals to catalyze hydrogenation reactions is known in the art. Because of the high cost of these catalysts and particularly of platinum, any method for increasing the activity and/ or life of the catalysts is desirable and valuable.

It has been found, generally, that heavy metals such as Pb, Cu, Bi, Ni and Cr or their ions either behave as poisons or have little effect on platinum group metal catalysts such as Pt, Pd and Rh used in hydrogenation reactions. Specifically, it has been found that Pb, Cu, Ni, Bi and Cr behave as poisons for Pt catalysts in the hydrogenation of nitrobenzene. Ag has been found to poison Pd catalysts in the hydrogenation of nitrobenzene, and it has also been found that the presence of Ag with Pt catalysts does not alter the rate of hydrogenation of ketones and olefins.

In accordance with the present invention, the organic nitrocompound, for instance an aromatic or aliphatic nitrocompound, is hydrogenated in liquid phase in the presence of a supported platinum catalyst and silver as promoter for the catalyst, the silver being distributed throughout the liquid without being alloyed with the platinum. By reason of the presence of the silver, both the activity and life of the platinum catalyst is materially increased or enhanced. Further, by reason of the increased activity of the catalyst due to the silver, hydrogenation of the nitro-containing compounds is carried out at a considerably faster rate than when supported platinum per se is employed as catalyst, to produce valuable products such as aromatic and aliphatic amines.

The process of this invention is especially advantageous for the production of aliphatic and aromatic amines by the reduction of the nitro group or groups of the corresponding nitro aliphatic or aromatic compounds. For example, aniline is obtained by the reduction of nitrobenzene, p-aminotoluene by the reduction of p-nitrotoluene, and n-propyl amine by the reduction of nitropropane. The nitro groups of polynitro organic compounds, such as dinitro and higher polynitro compounds, can be reduced in accordance with this invention as well as mono-nitro compounds to form the corresponding diamines or higher polyamines. polynitro compounds such as aromatic trinitro compounds should be conducted at a relatively low temperature to reduce the explosion hazard. The nitro aromatic compounds suitable as feed or charge stocks in the reduction process of this invention can be either the mononuclear aromatics or the polynuclear or polycyclic aromatics. These aromatic compounds, in addition to containing one or more nitro substituents, may also be substituted by groups which are not by themselves capable of reduction by hydrogen under the conditions utilized herein and which do not interfere with the reduction of the nitro groups, for instance groups such as alkoxy, hydroxy, amino, acyloxy, alkyl, and aryl groups. The nitro aliphatic compounds suitable as charge stocks herein, in addition to containing one or more nitro substituents, can also be substituted with groups incapable of being reduced under the conditions utilized in the instant process Hydrogenation of certain Patented May 24, 1966 and non-interfering with the reduction of the nitro groups,

for instance groups such as alkoxy, hydroxy, carboxy, amino, and aryl. Exemplary of the nitro-containing aromatic compounds suitable as charge stocks in this invention are Nitrobenzene, p-Nitrotoluene, m-Nitrotoluene, p-Nitrophenol, m-Nitrobenzoic acid, o-Nitrophenylacetic acid, p-Methoxynitrobenzene, m-Aminonitrobenzene, 4-Nitrobiphenyl, 4,4'-dinitrobiphenyl, 2,4-dinitrotoluene, and 2,6-dinitrotoluene.

Nitro-containing aliphatic compounds suitable as charge stocks herein include, for example,

l-nitroprop ane, l-nitrobutane, 2-nitrobutane, l-m'troisobutane, 2-nitroisobutane, 1-nitrobutanol-4, 1-nitro-5-methoxypentane, 1-nitro-4-phenylbutane, l-nitro-S-methoxypentane, 1-nitro-4-phenylbutane, 1-nitro-6-aminohexane, 3-nitro-butyric acid, and S-nitroethylbutyrate.

The Ag may be added in the form of a salt of an organic or inorganic acid, which is soluble or partially soluble in the reaction mixture. Less preferably, the Ag may be added in metallic form in the form of colloidal size particles with agitation during and after the addition to maintain the particles suspended throughout the reaction mixture. Examples of silver salts of inorganic acids which can be added are silver nitrate, silver nitrite, silver perchlorate and silver fluoride. Exemplary of the silver salts of organic acids are silver acetate, silver tartrate, silver b'enzoate and silver propionate.

While a silver salt which is only slightly soluble in the reaction mixture can be used, it is preferred to employ a soluble silver salt to facilitate distributing the silver in the reaction mixture.

The quantity of Ag utilized is determined by the amount of platinum metal present in the catalyst, and is utilized broadly within an atomic ratio range of about 0.05:1 to about 10:1 of Ag to Pt respectively. Although quantities greater than the about 10:1 upper limit of Ag to Pt can be utilized, if desired, such greater quantities of silver will provide little if any advantage and may be disadvantageous from an economic standpoint. Amounts of silver 'much below the about 0.05:1 lower limit of Ag to Pt should be avoided, as the promotional elfect desired will not be attained with these smaller amounts. The atomic ratio of Ag to Pt of 0.05:1 respectively may be provided, for instance when adding the Ag as AgNO and employing a Pt on carbon catalyst having a 5% Pt content, by adding 0.218 mg. AgNO per mg. of 5% Pt on carbon present. The atomic ratio of Ag to Pt of 10:1 respectively may be provided by adding 43.3 mg. AgNO per 100 mg. of 5% Pt on carbon. The preferred quantity of Ag for use herein is Within the ratio range of 0.37 atoms of Ag per atom of Pt to 3:1 of Ag to Pt respectively.

A solvent in which the nitro-containing organic compound is soluble or partially soluble is preferably employed. The solvent is an inert organic solvent, i.e. inert with respect to the nitro-containing compound, and in- 4 The flask was then placed in a shaking machine, connected to a gas burette with a leveling bulb, and alternately evacuated and flushed with hydrogen gas. The evacuation procedure was repeated at least 5 times. Then cludes for instance a carboxylic acid, for example acetic 5 the fiask was filled with hydrogen. The shaker, which acid, propionic acid, butyric acid or valeric acid; or an operated at 280 cycles per minutes, was started and the ester, for example ethyl acetate, propyl acetate or ethyl volume of hydrogen was measured on the burette at varipropionate, propyl propionate or methyl acetate. The ous intervals of time. The hydrogenation was run at carboxylic acid is preferred and acetic acid is preferred room temperature and atmospheric pressure. among such acids. The proportion of solvent employed Similar tests were run using nitrates of copper, nickel, can range, by weight, from an appreciable amount greater bismuth, chromium and silver instead of Pb(NO As than 0 percent to as high as 95 percent by volume, prefa basis for comparison, the same test was run without erably from about 25-90 percent solvent, the percentages adding heavy metal Salt to the Catalystbased on solvent plus organic nitrocompound. The results are tabulated in Table I and are expressed Temperatures employed in the hydrogenation of this in mlf H3 a r d i a 1 o 30 minut period. invention are in general within the range from about 0 7 Table C.400 C., preferably from about C.-100 C. The pressures employed in the hydrogenation can range from Activit sub-atmospheric to 3,000 p.s.i.g., preferably atmospheric 1111. m pressure t 100 pounds ptsig. 20 Catalyst Heavy Metal Salt mg. absorbed 15-30 The platinum can be supported on any suitable carrier, 1'ni.nutes e.g. carbon, alumina including activated alumina, kieselguhr, carbonates, for instance, calcium carbonate, barium 260 carbonate or strontium carbonate, sulfates, for instance barium sulfate, calcium sulfate or strontium sulfate, as- 5 mg.B l I(i1Il (I)O)a)-%H60 g3 bestos and s1l1ca. Carbon is the preferred carrier. The Do $5: R ZZ Z 240 carner may be m the form of powder, granules, ex- D0 3.9 mg. AgNOg 330 trusions, or pellets. The metal content of Pt on the support is usually, by weight, about 0.01-15 percent, Inthe-45minuteperi0d 515ml. ofH were absorbed. Inthesa.me Preferably about 1 5 percent. 3 period all other salts give alower activity thaninthe 15-30m1nnte period. The catalyst and silver promoter can be provided in The data in Table I indicates that of the metals tested, the hquid substrate for hydrogenation either by sepa- Ag was unique in its ability to accelerate the activity of rately adding the supported platinum catalyst and silver the Pt catalyst. promoter as described herein, or by adding to the liquid EXAMPLE H i g g i g igzlgg tai fi contamtmg In order to determine the effect of adding AgNO in This 22 St hi h C l ff 2. l g the hydrogenation of a nitro-containing compound, comreferred 2 3 len m e parative tests similar to the test described in Example I 5 n uid Whichpthe s y complgsles i were run utilizing 5% Pd on powdered carbon as cata insolubile orlsubstanfian i 5 mum i g t lyst and with the same substrates and solvents as used Hum catal St immersed 5. d e g f P a in Example I. A comparison of results with and Without romoter lor the catal st cilstii btited throu h dii f tl i the addition of Ag Shows that when no AgNO3 was added uivd without bein ed with th 1 g 440 ml. of H were absorbed in the 15-30 minute period. 1i uid i referibl g inert or a 1 F However, when 7.8 mg. of Ag. in the form of AgNO ousl for the g anic i; c g i was added, 315 ml. of H were absorbed in the comparable dro enated for instance tl ie carb ox lic a c id hr the 813 period' The results Show that the activity of the Pd T lae folldwing examples further illustrate the inver ition Catalyst was decreased by the addition of AgNO3' EXAMPLE I EXAMPLE III In order to illustrate the effect of variation of the In order to determine the efiect of various heavy metals ratio of AgzPt on the rate of hydrogenation, the results on Pt catalysts used in the hydrogenation of nitro-conof comparative tests are tabulated in Table II. The test taining compounds, comparative tests were performed. procedure was similar to that used in Example I.

Table II Mg. MI. E: Ex. Pt Catalyst Substrate Solvent AgNO absorbed 1--.--. 120 mg. 5% Pt on pow- 8.7 g. p-nitro- 100 ml. acetic 4 730 dered carbon. toluene. acid. 2 (lo o do 4 655 3..-.-- do. do do 4 675 2 a 0.. 0-. 6 0 -do do 8 705 7-.---. mg. 5% Pt on powdo do 0 195 dered carbon. 8 ..do do do 1 240 9 0 do do 2 290 10 do do -do 4 235 11.-. 0 d0 do 8 235 A 1 liter heavy wall Earlenmeyer flask was charged Experiments 1-6 show the efl'ect of adding various with catalyst, substrate and solvent in the following amounts of silver nitrate. Experiments 13 are triplimanner: 120 mg. of 5% Pt on powdered carbon was cates and show the general precision of the method. The placed in the flask. To this was added 7.6 mg. of reproductiveness of these experiments with Ag is some- Pb(NO Then 3 ml. of nitrobenzene and 8.7 g. of thing less than is usually found in this kind of rate measp-nitrotoluene in ml. of acetic acid were added to urement. Nonetheless all of the catalysts with silver and the flask. 7 employing mg. 5% Pt/C as catalyst (experiments 13, 5 and 6) are about 60% more active than the unpromoted catalyst (experiment 4). Within the range studied, 2-8 mg. AgNO with 120 mg. of 5% Pt/C and up to 8 mg. of AgNO with 60 mg. of 5% Pt/C, the proent invention without departing from the spirit thereof, and the invention includes all such modifications.

What is claimed is:

1. A process for the catalytic hydrogen reduction of motional effect was large. The atoms of Ag/atom Pt for 5 at least one organic nitrocompound selected from the 2 mg. AgNO 4 mg. AgNO and 8 mg. AgNO per 120 group consisting of nitrobenzene, p-nitrotoluene, m-nimg. of 5% Pt/C are approximately 0.37, 0.75, and 1.5. trotoluene, m aminonitrobenzene, 4 nitrobiphenyl, For 8 mg. AgNO per 60 mg. 5% Pt/C the ratio is ap- 4,4 dinitrobiphenyl, 2,4 dinitrotoluene, and 2,6- proximately 3:1. dinitrotoluene, 1 nitropropane, 1 nitrobutane, 2 The results of experiments 7-11 further evidences the nitrobutane, 1 nitroisobutane, 2 nitroisobutane, 1- promotional efiects of the silver. nitrobutanol 4, 1 nitro 5 methoxypentane, 1-nitro- EXAMPLE 1V 4 phenylbutane, 1 nitro 6 ammohexane, 3 mtrw butymc acid and 3-mtroethylbutyrate, to form the corre- In order to illustrate the effect of the use of Ag with sponding amino compound, which comprises contacting a Pt catalyst on the hydrogenation of nitro-containing the selected nitrocompo und in liquid phase in the prescompounds when the substrate, solvent and Pt catalyst ence of hydrogen and at hydrogenating conditions of are varied, results of comparison tests are reported in temperature and pressure within the range from about Table HI. The test procedure Was similar to that used 0 C.400 C. and subatmosphetric to 3000 p.s.i.g., rein Example I. The catalyst, substrate and solvent were spectively, with platinum as catalyst supported on a catavaried and comparison tests were run with and without lyst carrier and silver as promoter for the catalyst, the the addition of Ag. The catalyst, substrate and solvent silver being distributed throughout the liquid without used for each test and the quantities used are shown in being alloyed with the platinum. the table. The results are reported in Table HI as ml. of 2. The process of claim 1 wherein the silver is present H absorbed in a given period of time, as indicated. in the liquid in amount within the atomic ratio range of Increased hydrogenation rates by added Ag are not due about 0.05:1 to about 10:1 of Ag to Pt respectively.

Table 111 Ml. H Ex. Pt Catalyst AgNO Substrate Solvent 15-30 mg. Minutes 1 120 mg. 5% Pt on Carbon N0. 1 0 3.5ml. NO2, 8.7g. p-nitrotoluene--- 100 ml. acetic aeid 1 220 2 do 4 .do 330 t 4 2ml.acetophenone 10 4 0 tin 10 5 4 4ml.octene-1 100 s 0 .....de 100 7 4 50ml.NO 95 8 0 rln 70 o 4 8.7 g p-nitrotoluene 675 0 --do 440 4 do 0 4 3.5ml.NO 360 0 3.0 ml. N02, 8.7 g. p-nitrotoluene. 760 Q 4 ...-.d0 955 of 5% Pt on A120; 0 8.7 g. p-nitrotolueue 150 n 6 .....do 230 of 5% Pt on Carbon No. 1-.- 0 3.5 ml. nitropronane 10 do 4 do 20 0 3.5111145N02 100 ml. ethyl acetate 190 4 do do 240 1 This means no 15 minute period higher than 220 ml. Hg absorbed (maximum).

'- 515 maximum -45 minute period. 3 N0 platinum.

to any catalytic activity of the Ag itself. This is shown 3. The process of claim 1 wherein the silver is present by comparing experiments 9, 10 and 11 of foregoing in the liquid in amount within the atomic ratio range of Table III. In the absence of Pt (experiment 11), the Ag showed zero activity. The promotional eifect of Ag is not limited to Pt on any one type of carbon. The improved rate is attained with carbon No. 1 in experiments 1 and 2 of Table III, and also with carbon No. 2 as carrier in experiments 13 and 14 of Table III. Carbon No. l is an unwashed carbon and carbon No. 2 an acid washed carbon. The carrier for the Pt is of course not limited to carbon but includes the other carrier materials hereinbefore disclosed. Experiments 15 and 16 of the Table III show the promotion of Pt by Ag on other carriers than carbon. In these two experiments with Pt on powdered A1 0 a 53% increase in rate was obtained by the addition of silver.

The increased activity of the Pt catalyst as a result of the addition of the Ag was observed when the substrate was an aromatic nitro-containing compound (experirnents 1, 2, 7, 9, 12, 14, 16 and 20 of Table III), and an aliphatic nitro-containing compound (experiment 18 of Table III). However, the rate of hydrogenation of the non-nitrocontaining compounds, acetophenone and octene-l, was unaltered by the addition of Ag. (experiments 3 and 5 of Table HI).

It will be obvious to those skilled in the art that many modifications may be made within the scope of the pres- References Cited by the Examiner UNITED STATES PATENTS 2,802,889 8/1957 Frevel et al. 260-677 2,857,337 10/1958 Hamilton et al. 252472 2,967,200 l/1961 Foster et al. 260566 2,967,835 l/1961 Hort 252447 FOREIGN PATENTS 297,212 9/1928 Great Britain.

MAURICE A. BRINDISI, Primary Examiner.

S. T. OZAKI, DALE R. MAHANAND,

Assistant Examiners. 

1. A PROCESS FOR THE CATALYTIC HYDROGEN REDUCTION OF AT LEAST ONE ORGANIC NITROCOMPOUND SELECTED FROM THE GROUP CONSISTING OF NITROBENZENE, P-NITROTOLUENE, M-NITROTOLUENE, M - AMINONITROBENZENE, 4 - NITROBIPHENYL, 4,4'' - DINITROBIPHENYL, 2,4 / DINITROTOLUENE, AND 2,6DINITROTOLUENE, 1 - NITROPROPANE, 1 - NITROBUTANE, 2 NITROBUTANE, 1 - NITROISOBUTANE, 2 - NITROISOBUTANE, 1NITROBUTANOL-4, 1 - NITRO - 5 - METHOXYPENTANE, 1-NITRO4 - PHENYLBUTANE, 1 -NITRO - 6 -AMINOHEXANE, 3 - NITROBUTYRIC ACID AND 3-NITROETHYLBUTYRATE TO FORM THE CORRESPONDING AMINO COMPOUND, WHICH COMPRISES CONTACTING THE SELECTED NITROCOMPOUND IN LIQUID PHASE IN THE PRESENCE OF HYDROGEN AND AT HYDROGENATING CONDITIONS OF TEMPERATURE AND PRESSURE WITHIN THE RANGE FROM ABOUT 0*C.-400*C. AND SUBATMOSPHERIC TO 3000 P.S.I.G., RESPECTIVELY, WITH PLATINUM AS CATALYST SUPPORTED ON A CATALYST CARRIER AND SILVER AS PROMOTER FOR THE CATALYST, THE SILVER BEING DISTRIBUTED THROUGHOUT THE LIQUID WITHOUT BEING ALLOYED WITH THE PLATINUM. 